Fused filament fabrication is a 3D printing process that uses a continuous filament of material, typically a thermoplastic that is dispensed, or extruded, from a print head that moves in three dimensions under computer control to manufacture a part. Current fused filament fabrication machines “print” parts by sequentially stacking two-dimensional layers on top of each other. This stacking, or layering, of layers limits the complexity of parts that can be manufactured by such machines.